McKinsey’s survey also includes people who bought insurance outside the new marketplaces.

That's right...the McKinsey study (and I'm assuming the earlier one) doesn't distinguish between people who enrolled via the ACA exchanges and those who enrolled directly/off-exchange.

Sure enough, when you go to page 8 of the survey, you get this glossary definition:

Select new 2014 product: Either previously insured respondents who switched (either switching from one carrier to another, or switching policies but staying with the same carrier), or previously uninsured who enrolled; policies can be selected on or off exchange; includes those who paid their premium and those who hadn’t yet at time of survey.

This is important for a couple of reasons.

The new study was done in mid-February, when exchange QHP enrollments stood at roughly 3.6 million.

However, we have no idea how many off-exchange enrollments there have been since October. I know of at least 460,000, but it's almost certainly 2-3 million at a minimum, probably more.

So, to simplify, let's call it 3.6 million exchange-based and anotherh 3.6 million off-exchange enrollments as of mid-February.

27% of 7.2 million is around 1.94 million people previously uninsured and 5.26 million already covered.

However, without distinguishing between the two, it's entirely possible that practically all 3.6 million of the direct enrollments were people who were already covered, leaving only 1.66 million of the exchange-based QHPs already covered.

This would mean that instead of 27%, the actual number of ACA EXCHANGE QHPs that were previously uninsured is closer to 54%.

Of course, I have no way of knowing this. It could theoretically be closer to the opposite extreme--perhaps only 1% of exchange QHPs didn't have insurance before (well, except that NY accounts for around 7% of the total enrollments by itself, which means it's a minimum of around 4%).

Conversely, for all we know, there may have been 6 or 7 million off-exchange enrollments as of mid-February, which could mean that the exchange QHPs are closer to 100% previously uninsured (again, I doubt this as well).

The point is that by mixing the two groups together, McKinsey's study tells us pretty much...nothing.